Rescue workers check through rubble in the northern Syrian city of Aleppo on Feb. 12. / Fadi Al-Halab, AFP/Getty Images

by Oren Dorell, USA TODAY

by Oren Dorell, USA TODAY

Syria peace talks are on the verge of collapse as the war heads into its fourth year, raising the prospect of a vicious conflict lasting years and plunging border states into chaos that only Western military intervention can snuff out, say analysts.

United Nations negotiators were pessimistic this week that a deal can be struck between dictator Bashar Assad and the anti-regime rebels. Western nations that publicly deplore the violence have no Plan B to end it.

On Thursday, at least 51 people died in a single day of Syrian government airstrikes and shelling of opposition-controlled districts of Aleppo, activists said.

Some suggest it may be OK for American adversaries such as Assad, al-Qaeda, Iran and Hezbollah to stay bogged down in an interminable war, in which 130,000 people have died and nearly 6 million Syrians have been forced from their homes.

But as the West stands on the sidelines, Syria is becoming a proving ground for Islamic terror factions fighting Assad and churning out battle-hardened jihadists on orders to infiltrate neighboring states, analysts say. Iraq and Lebanon are boiling from Syrian militancy, and more states may follow if the war continues.

"Letting the fighting continue indefinitely and letting al-Qaeda and the Iranians split the country between them, that's not a good outcome," says Max Boot, an analyst at the Council on Foreign Relations.

"Syrian soil would become a launching pad for Iranian interests in the region and a launching pad for al-Qaeda, which is a grim outcome," he said.

U.S. or NATO "boots on the ground" may be the only way to stop Syria from becoming an al-Qaeda safe haven, or worse, an anti-American axis of a nuclear Iran aligned with a brutal Syrian regime and a missile-laden Hezbollah in Lebanon, Boot says.

None of the major factions fighting in the Syria civil war â?? the Assad regime, affiliates of al-Qaeda, the Free Syrian Army rebels â?? appears to be any closer to dominating and ending the war that began in March 2011.

Zachary Keck, an associate editor for The Diplomat, a foreign affairs magazine for the Asia-Pacific region, says the United States is winning in Syria by standing by.

The war costs Iran billions of dollars, Hezbollah has lost hundreds of fighters and both have lost standing in the Arab world because of their support of the slaughter of Sunnis, he says.

"From a purely strategic standpoint, no country has benefited more from the horrible tragedy in Syria than the United States," Keck says.

WIDESPREAD WAR

A war that began when the Syrian military fired on peaceful demonstrations against the regime's treatment of detainees has become one of the longest conflicts in the Middle East, sucking in radicals, sheiks and superpowers on all sides.

Assad's military has targeted neighborhoods indiscriminately with artillery and airstrikes. "Barrel bombs," containers filled with fuel and explosives, are shoved out of military aircraft daily onto cities.

In rebel-held cities such as Aleppo, once Syria's economic capital, the Assad regime has a policy of "surrender or starve," blocking food from communities unless they turn over weapons and fighters. Non-combatant children and adults are starving, according to the Red Cross.

Militants and Muslim terrorists have flooded into the fight from the Middle East, Chechnya, Africa and Europe. The number of al-Qaeda-linked fighters in Syria has mushroomed from 2,000 to more than 30,000 in two years, Israeli intelligence agencies tell the Associated Press.

Police in Norway charged a citizen with terror offenses allegedly committed in Syria - the first such case in the Scandinavian country, the Associated Press reported Thursday. Security Police spokesman Martin Bernsen said that the 22-year-old man of Pakistani background was arrested Friday on his return to Oslo from Syria.

Syrian military deserters who banded together to form the Free Syrian Army have notched victories over Assad's bases but have failed to hold on to their gains as the Assad forces redeploy from hot spot to hot spot with heavy cannons and air assaults the rebels cannot repel.

Backed by Russia, Iran and Hezbollah, Assad has access to a steady supply of fuel, ammunition and fighters.

Peace talks in Vienna, sponsored by the United Nations and the Obama administration, are deadlocked over whether Assad can remain a part of the country's future. U.N. mediator Lakhdar Brahimi said Tuesday that the talks between the Syrian government and opposition "are not making much progress."

WESTERN HESITATION

Rebels have sought outside help to bring about regime change and end the conflict, calling for heavy weapons and airstrikes to neutralize Assad's tanks and air force.

President Obama has rebuffed calls for more robust action, and Fawaz Gerges, director of the Middle East Center at the London School of Economics, says Europe is unlikely to get involved without U.S. involvement.

"The U.K.'s Parliament has spoken," he said, referring to London's rejection of military action against Assad in August. "There is no European country that would take the lead."

The inaction of the West is taken advantage of by affiliates of al-Qaeda, which aims for a rigid Islamic state in a Middle East cleansed of Jews and competing Muslim sects.

U.S. intelligence chiefs say al-Qaeda's growth in Syria is a threat to the USA. Director of National Intelligence James Clapper said 75,000 to 110,000 fighters are taking part, 26,000 of which are "extremists," and 7,000 are foreigners from the Middle East and Europe.

"We're seeing now the appearance of training complexes in Syria to train people to go back to their countries and, of course, conduct more terrorist acts," Clapper told the Senate Select Committee on Intelligence last month.

A study by the Tel Aviv-based Meir Amit Intelligence and Terrorism Information Center found that 15% of all suicide bombings in the world took place in Syria in 2013. Many attacks displayed "a high level of sophistication and professionalism," according to the study first reported in The Jerusalem Post.

The study found that the terrorist innovation honed in Syria of several bombers going after high-value targets simultaneously is showing up in al-Qaeda attacks elsewhere in the Middle East.

Shlomo Brom, an analyst at Israel's Institute for National Security Studies, says Syria looks a lot like Afghanistan before the Sept. 11 terrorist attacks and may require the same action taken by President George W. Bush and the U.S. Congress.

"I don't need to remind you that the United States invaded Afghanistan to deny terrorists this kind of shelter," Brom says.

Boot says Obama's approach to the conflict (removing Assad's chemical weapons and promoting peace talks) increases the chance that the U.S. military will be dragged into the Middle East in a major way.

The battlefield stalemate in Syria is creating cadres of jihadists who stream out into other Sunni states and even European countries, says Boot, author of Invisible Armies, a history of guerrilla forces.

Islamic terrorists from Syria have infiltrated Iraq, setting off suicide car bombs and grabbing a toehold in the major Sunni cities of Fallujah and Ramadi. This week, militants attacked an Iraqi army barracks in Ayn al-Jahish outside the northern city of Mosul and killed 15 troops, beheading eight of them.

Al-Qaeda terrorists have gotten Iraqis to join them against the U.S.-backed Shiite government in Baghdad in an insurgency not unlike the one put down by the U.S. military in 2008.

In Lebanon, radicals from Syria have launched attacks and assassinations against Hezbollah, provoking counterattacks that could blow up into full-scale war, according to the government in Beirut.

Lebanese Sheik Bilal Dokmak, a cleric who raises money for the Free Syrian Army, says he supports jihad in Syria but not in Lebanon.

"The U.S. government's permissive approach to Assad allows for the extension of the conflict in Syria and nearby countries," Dokmak said in Beirut.

"The longer you let a civil war go on, the more empowerment of radicals on both sides, and that's the last thing we want to see," Boot said.

Keck said the battle hurts the radicals. He said al-Qaeda's Iraqi affiliate, the Islamic State of Iraq and Syria, has been weakened in the eyes of Sunni Arabs worldwide by turning its guns on Sunni Muslim rebel groups it considers impious.

Former U.S. ambassador Ryan Crocker sees empowerment of al-Qaeda as the worst outcome and said Obama should back Assad, not try to force him out.

"You could have a major Arab capital in the hands of al-Qaeda, something they've always sought," Crocker said.

Crocker said the United States should press allies Saudi Arabia and Qatar to cut the money and arms they buy for the rebels, because too much of it reaches al-Qaeda.

"Since Assad is not going away, we should be talking to second- or third-echelon individuals" in his regime about the next step, said Crocker, who has held ambassadorships in Lebanon, Iraq and Afghanistan.

POWER STRUGGLE

Despite the regime's advantages and rebel fatigue, the rebels aren't going away, said Valerie Szybala, an analyst at the Institute for the Study of War.

"The regime outarms, outguns the rebels, it has air power and more advanced weapons, but that doesn't stop a guerrilla insurgency focused on disrupting regime supplies, transport and aircraft," Szybala said. "The rebels' ability to do that hasn't been diminished."

Crocker said the United States should help Assad defeat al-Qaeda factions in the country.

But that could allow Iran to claim a victory over the U.S.-allied Sunni Arab Gulf states, increasingly frantic that the Shiites of Iran, Syria and Hezbollah will replace the United States as the dominant power in the Middle East.

Tony Badran, an analyst at the Foundation for Defense of Democracies, said Iran has already provided support to Shiite uprisings in Yemen and Bahrain. Should Assad prevail in Syria, Badran said, Iran will believe it can interfere in other Arab countries and "nobody cares to get in its way."